1. Field of the Invention
The present invention relates to an improvement in a coking process.
2. Description of the Prior Art
Fluid coking is a well-known process. See, for example, U.S. Pat. No. 2,881,130, the teachings of which are hereby incorporated by reference. The fluid coking process can be conducted with or without recycle of the heavy constituents of the coking product. Integrated fluid coking and coke gasification processes are also known and disclosed, for example, in U.S. Pat. Nos. 3,702,516; 3,759,676; and 4,325,815, the teachings of which are hereby incorporated by reference.
Delayed coking is a well-known process in which a hydrocarbonaceous oil is heated to a coking temperature and then passed into a coking drum to produce a vapor phase product, including liquid hydrocarbons and coke. See Hydrocarbon Processing, September 1980, page 153.
The present invention is applicable to conventional fluid coking processes as well as to integrated fluid coking and gasification processes and to delayed coking.
U.S. Pat. No. 4,057,487 discloses a fluid coking process in which the heavy oil stream separated from the coker products in a scrubbing zone is passed to a vacuum distillation zone and a vacuum distillation zone bottoms fraction is recycled to the coking zone.
U.S. Pat. No. 2,777,802 discloses, in FIG. 2, a fluid coking process in which the total coker overhead product is subjected to extractive distillation to remove metal contaminants. A bottoms product from the extractive distillation zone may be recycled to the coking zone.
It is known to recycle coker-derived naphtha to the coking zone. See, for example, U.S. Pat. No. 2,734,852; U.S. Pat. No. 2,742,518.
U.S. Pat. No. 4,354,928 discloses deasphalting hydrocarbon oils utilizing a solvent which may be a coker naphtha (see column 2, line 48).